Valve spring concerns: Coil bind height, Seat pressure, Lifter weight, Pushrod weight, Rocker arm ratio, Valve weight, RPM range and limit. As each is critical, and non forgiving, you do need to know them. When you changed the intake valve size, you made a difference to the demand on the spring. That spring is the only thing that keeps the valve in time with the cam and piston. For practical reasons the difference is small and the engine is mostly stock. You will get by with the valve springs that have been recommended. I would Have the shop measure the height at full lift and keep around 0.060 left in the spring to prevent coil binding at the high end. The higher the RPM range the more critical these things become. Many engines that can turn around 6,000 RPM have 2 springs, one inside the other. Why 2? To prevent spring harmonics from allowing the valve to lose contact with the cam, otherwise known as valve float. Most commonly followed by contact with the piston. Rapid disassembly can follow. So to completely get the answer you need to do a lot of work. Most cam companies have done the work for you so I would use them for advice. With these things in mind, the advice from Hotrod is as good as it gets. Not a critique, just an old guy letting you know there are lots of things that Engineers do besides drive trains.
